In general, as an electrolyzed water-manufacturing apparatus, there are an apparatus having a diaphragm type electrolysis tank with a diaphragm between a pair of electrodes and an apparatus having a non-diaphragm type electrolysis tank without a diaphragm. These apparatuses are used according to an object.
For the diaphragm of the diaphragm type electrolysis tank, an ion-exchange membrane which is a charged membrane, a neutral membrane which is an uncharged membrane, or the like is used. Acidic electrolyzed water is generated on an anode side (anode chamber) of the diaphragm type electrolysis tank, and alkaline electrolyzed water is generated on a cathode side (cathode chamber). When an apparatus having a diaphragm type electrolysis tank is used, usually, water generated by electrolysis on an anode side (anode water) and water generated by electrolysis on a cathode side (cathode water) are extracted separately.
When electrolysis is performed by adding a chloride such as sodium chloride as an electrolyte to electrolysis starting water, hydrochloric acid, hypochlorous acid, dissolved oxygen, or Reactive Oxygen Species such as a hydroxyl radical, which is an electrode reaction product, is generated in anode water. Hypochlorous acid exhibits a strong chlorination reaction and oxidation reaction. Therefore, anode water is used for sterilization of fungi or the like.
On the other hand, cathode water generated on a cathode side is known widely as alkali ion water for drinking. A cathode water water-manufacturing apparatus (for example, refer to Patent Literatures 1 to 3) is commercially available as a medical equipment or the like, and is widespread with spread of mineral water.
Properties of the water generated by electrolysis can be expressed by some parameters. Examples of the parameter include a pH value, an oxidation-redox potential, a dissolved oxygen concentration, a dissolved hydrogen concentration, and a hypochlorous acid concentration. The values of these parameters are determined by the type and concentration of a solute contained in electrolysis starting water, the magnitude of an electrolytic energy imparted to electrolyzed water, and the like.
When water generated by electrolysis is used for drinking, the most important parameters are a hypochlorous acid concentration and a pH value. Cathode water does not contain hypochlorous acid, and therefore only the pH value should be considered. Strongly alkaline electrolyzed water or strongly acidic electrolyzed water is dangerous to a living body, and therefore electrolyzed water in a weakly alkaline to weakly acidic region is used for drinking. When the electrolytic energy is large, anode water shifts to a strongly acidic side, and cathode water shifts to a strongly alkaline side. Therefore, usually, an excessively large amount of electricity cannot be used at the time of electrolysis.
In order to maintain the pH of electrolyzed water obtained by using a large amount of electricity at the time of electrolysis within a predetermined range, various methods have been used conventionally. For example, a method for removing a harmful substance such as hypochlorous acid after obtaining mixed electrolyzed water by electrolysis with a non-diaphragm type electrolysis tank or by mixing anode water and cathode water obtained by electrolysis with a diaphragm type electrolysis tank; and a method for controlling the pH of cathode water by adding a pH adjuster before or after electrolysis with a diaphragm type electrolysis tank (refer to Patent Literature 4) are known. However, when electrolysis is performed by adding vitamin C or polyphenol to electrolysis starting water, an oxidation reaction in an anode chamber cannot be avoided disadvantageously.